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Timing chain - when to replace?

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J

jackag91

Jedi Warrior
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While I am taking my engine (TR6) apart, I am trying to build a shopping list.

Everything has looked good so far... I think I might need to replace the tappets (maybe)

How can I tell if I need to replace the timing chain and gears? I checked the Haynes book and it just says if moves .40 inches from a straight line.

Is that a straight line while under tension? While it is on the car?

Is there a rule of thumb for the gears? Or should I just be safe and replace them?
 
Cheap insurance. Do it - gears, too!

Mickey
 
The traditional test for the chain is to hold one side horizontal, and see how far the other side droops. I would guess that's the .40 the Haynes is talking about.

Personally, with all the horror stories of bad parts on the market, I prefer to keep the original ones if they are serviceable. This "new" sprocket has only a few thousand miles on it:
 
TR3driver said:
...

Personally, with all the horror stories of bad parts on the market, I prefer to keep the original ones if they are serviceable. This "new" sprocket has only a few thousand miles on it:
Click to expand...

I talked to Ken at BF&E about this, as I was ordering parts from him for the engine rebuild. He told me that if what you have is in good shape, just go ahead and use it. I wound up using both gears, the chain and the tensioner over again.
 
ok, tr3driver, tell me who made that timing sprocket. I hope it is not the same as the one i plan to use that is made in Germany.
thanks
Rob
 
trfourtune said:
ok, tr3driver, tell me who made that timing sprocket.
Click to expand...
Sorry, no can do. It's not a secret, just that no one knows at this point. Not my engine (thank Goodness!) and the owner had someone else rebuild it almost 10 years ago now. He said there was no maker ID on the sprocket.

Besides, as often as bad parts come and go, it's not likely that a sprocket from the same maker today would have the same problem. I don't believe anyone is deliberately making bad parts, just that there are sometimes bad batches of them. Or even batches with just a few bad parts in them.

Problem is, once a vendor gets a batch of bad parts, the pressure is enormous for them to sell the parts anyway. Even if 50% of the parts are bad, the vendor loses less money replacing bad parts than throwing the entire lot away. And I don't believe any vendor is equipped for 100% testing, even if they could afford to do it.

On a related note, anyone know how to build a Rockwell C hardness tester?
 
TR3driver said:
...

On a related note, anyone know how to build a Rockwell C hardness tester?
Click to expand...

I often thought about getting a hardness tester for use at work, but finally just got a set of hardness testing files. They aren't the perfect solution, but they do get you in the ballpark for the few times that I need to test for hardness.
 
trfourtune said:
ok, tr3driver, tell me who made that timing sprocket. I hope it is not the same as the one i plan to use that is made in Germany.
thanks
Rob
Click to expand...


Germany, via Taiwan. Like County Brand, UK company, made in India, for the most part.

I changed my timing chain, gears and related parts just because.
 
martx-5 said:
I often thought about getting a hardness tester for use at work, but finally just got a set of hardness testing files.
Click to expand...
Not bad at all ... any idea what they cost? I couldn't find the info on the web site.
 
Thanks, Art.
 
Hi,look for any sign of wear on the drive side of the teeth on the gears and any loosness in the chain. I would change the timing chain ,gears and tensioner as a matter of course having stripped the engine thus far. With a good recognised make.What was the original reason for the strip down?
 
Trbill,
"Germany, via Taiwan. Like County Brand, UK company, made in India, for the most part."
I think if a part has "Germany" stamped on it, it is made in Germany. I don't think, by law, the makers are allowed to stamp a part with a different contry of origin other that where it is made.
Boxes, however, can have all kinds of misleading information on them. usually if there is no contry of origin stamped on the part, then you have no idea where it came from.
Yes, hardness tester would be great.
trfourtune
 
oops, tr6bill,
sorry.
 
Hi Folks,

Being something of a "Metallurgist"; Its pretty darn obvious that the "Mat`l" itself is way "TOO SOFT".

These parts would typ. be "Cased Hardened" to a specific depth. These sprockets obviously have very little or no case hardening whatsoever.

Bad parts are not necessarily mfg. wrong but someone here should have checked the Rc (Rockwell Hardness) before machining.

Relative to getting a Rockwell Tester; I`ll try and find out where you can get one. I know several Industrial Supply houses that could probably supply one.

Will advise later,

Russ
 
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